System and process of capturing carbon dioxide from flue gases

ABSTRACT

A system and a process for capturing Carbon Dioxide (CO 2 ) from flue gases are disclosed. The process comprises feeding a flue gas comprising CO 2  to at least one Rotary Packed Bed (RPB) absorber rotating circularly. A solvent may be provided through an inner radius of the RPB absorber. The solvent may move towards an outer radius of the RPB absorber. The solvent may react with the flue gas in a counter-current flow. The process further includes passing the flue gas through at least one of a water wash and an acid wash to remove traces of the solvent present in the flue gas. Finally, the solvent reacted with the CO 2  may be thermally regenerated for re-utilizing the solvent back in the process.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. 119 to previouslyfiled Indian Patent Application No. 2018-11023872, filed 26 Jun. 2018,and U.K. Patent Application No. 1813839.6, filed 24 Aug. 2018, thecontents of which are incorporated herein by reference in theirentirety.

FIELD OF THE DISCLOSURE

The present disclosure is generally related to a chemical process andmore particularly related to a process of capturing carbon dioxide fromflue gases.

BACKGROUND

The subject matter discussed in the background section should not beassumed to be prior art merely as a result of its mention in thebackground section. Similarly, a problem mentioned in the backgroundsection or associated with the subject matter of the background sectionshould not be assumed to have been previously recognized in the priorart. The subject matter in the background section merely representsdifferent approaches, which in and of themselves may also correspond toimplementations of the claimed technology.

FIG. 1 illustrates a block diagram 100 of a conventional process forcapturing Carbon Dioxide (CO₂) from flue gases. CO₂ is separated from amixture of gases, using a solvent which selectively reacts with the CO₂.After the CO₂ has reacted with the solvent, the solvent can beregenerated using heat to release the CO₂ and regenerate the solvent forfurther CO₂ processing. A flue gas 102 containing CO₂ is contacted witha liquid solvent in a static packed column 104. The liquid solvent iscascaded over a top of the static packed column 104 and falls undergravity to a bottom where it is collected in a sump.

A second static packed column 106 having structured packing compriseswash stages to remove traces of the solvent and volatile chemicals. Agaseous mixture depleted of CO₂ passes through the wash stages to removetraces of the solvent and volatile chemicals formed through degradationreactions of the solvent components. Thus, the flue gas 108 depleted ofCO₂ is released from the top of the static packed column 104. All of thewash stages occur in similar static structured packing and use water oracid for washing.

The solvent is fed into a top section of a stripper column 112 andallowed to fall under gravity over a packing material to a bottom of thestripper column 112. At the bottom, the solvent is drawn into a reboiler114. Inside the reboiler 114, the solvent is heated to a temperature sothat at an operating pressure of the stripper column 112, water presentin the solvent gets vaporized to steam. The steam and the CO₂ rise to atop of the stripper column 112 where a condenser cools the steam and gasto around 40° C. This condenses the steam into water 116 and gaseous CO₂118. The condensed water 116 is returned to the top of the strippercolumn via reflux drum 120 and the gaseous CO₂ 118 used for downstreamprocesses while the solvent at the bottom of the stripper is recycled toan absorber as a lean solvent via the heat exchanger 110, ready torepeat the absorption process again.

Utilization of static packed columns in conventional processes providesinefficient mixing of the CO₂ present in flue gases and is limited bythe gravitational force under which the solvent flows, thus limiting themass transfer with solvents and during the water and acid washes.Further, the large size of static packed columns used in conventionalprocesses require vast amounts of space and lead to high installationand operational cost of the system. Thus, an improved system and processfor capturing CO₂ from flue gases are much desired.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings illustrate various embodiments of systems,methods, and embodiments of various other aspects of the disclosure. Anyperson with ordinary skills in the art will appreciate that theillustrated element boundaries (e.g., boxes, groups of boxes, or othershapes) in the figures represent one example of the boundaries. It maybe that in some examples one element may be designed as multipleelements or that multiple elements may be designed as one element. Insome examples, an element shown as an internal component of one elementmay be implemented as an external component in another and vice versa.Furthermore, elements may not be drawn to scale. Non-limiting andnon-exhaustive descriptions are described with reference to thefollowing drawings. The components in the figures are not necessarily toscale, emphasis instead being placed upon illustrating principles.

FIG. 1 illustrates a block diagram 100 of a conventional process forcapturing Carbon Dioxide (CO₂) from flue gases, according to the priorart.

FIG. 2 illustrates a block diagram 200 of a system for capturing CarbonDioxide (CO₂) from flue gases, according to an embodiment.

FIG. 3A illustrates a block diagram 300 illustrating functioning of aRotary Packed Bed (RPB) absorber 302 in a system for capturing CarbonDioxide (CO₂) from flue gases, according to another embodiment.

FIG. 3B illustrates a block diagram 3000 illustrating functioning of aRotary Packed Bed (RPB) absorber 3020 in a system for capturing CarbonDioxide (CO₂) from flue gases.

FIG. 4A illustrates a block diagram 400 representation of a vacuumsolvent reclamation system, according to an embodiment.

FIG. 4B illustrates a block diagram 4000 representation of a vacuumsolvent reclamation system, according to an embodiment.

FIGS. 5A and 5B illustrate a flowchart 500 illustrating a process ofcapturing Carbon Dioxide (CO₂) from flue gases, according to anembodiment.

FIG. 6 illustrates a block diagram 600 representation of a Rotary PackedBed Absorber

FIG. 7 illustrates a graph showing vapor liquid equilibrium (VLE)relationship between partial pressure of CO₂ in the vapor phase and theloading (i.e. concentration) of CO₂ in a solvent at 40 C.

FIG. 8 illustrates a design of a system 1200 for capturing 10 tons ofCO₂ per day.

DETAILED DESCRIPTION

Some embodiments of this disclosure, illustrating all its features, willnow be discussed in detail. The words “comprising,” “having,”“containing,” and “including,” and other forms thereof, are intended tobe equivalent in meaning and be open ended in that an item or itemsfollowing any one of these words is not meant to be an exhaustivelisting of such item or items, or meant to be limited to only the listeditem or items.

It must also be noted that as used herein and in the appended claims,the singular forms “a,” “an,” and “the” include plural references unlessthe context clearly dictates otherwise. Although any systems and methodssimilar or equivalent to those described herein can be used in thepractice or testing of embodiments of the present disclosure, thepreferred systems and methods are now described.

According to a first aspect of the present disclosure, there is provideda process of capturing Carbon Dioxide (CO₂) from flue gases, the processcomprising the step of: feeding a flue gas comprising CO₂ to at leastone Rotary Packed Bed (RPB) absorber rotating circularly, wherein asolvent provided through an inner radius of the at least one RPBabsorber moves towards an outer radius of the at least one RPB absorber,and wherein the solvent reacts with the flue gas in a counter-currentflow.

Preferably, wherein the process further comprises the step of: thermallyregenerating the solvent reacted with the CO₂ for re-utilizing thesolvent in the process.

Further preferably, wherein the process further comprises the step of:passing the flue gas through one or both of a water wash and an acidwash to remove traces of the solvent present in the flue gas;optionally, wherein one or both of the water wash and the acid wash areconducted on separate Rotary Packed Beds (RPBs).

Advantageously, wherein a housing of the RPB or RPBs is mounted on arotatable disk.

Preferably, wherein the step of feeding a flue gas comprising CO₂ to atleast one Rotary Packed Bed (RPB) absorber rotating circularly comprisesfeeding the flue gas to two, three, four, five or six Rotary Packed Bed(RPB) absorbers rotating circularly.

Further preferably, wherein the two, three, four, five or six RotaryPacked Bed (RPB) absorbers rotating circularly are arranged in series ona common shaft.

Advantageously, wherein the solvent reacts with the flue gas in acounter-current flow to remove CO₂ from the flue gas and form CO₂ richsolvent.

Preferably, further comprising the step of: passing the CO₂ rich solventto a stripper, wherein the stripper acts to strip CO₂ from the CO₂ richsolvent forming CO₂ lean solvent.

Further preferably, wherein the stripper is a stripper column; or, astripper static column; or, an RPB stripper.

Advantageously, wherein the CO₂ lean solvent is re-introduced into theat least one Rotary Packed Bed (RPB) absorber rotating circularly.

Preferably, further comprising the step of: passing CO₂ rich solventleaving the at least one Rotary Packed Bed (RPB) absorber to a RotaryPacked Bed (RPB) O₂ eliminator; or, a static packed bed O₂ eliminator;and eliminating dissolved O₂ from the solvent.

Further preferably, wherein the step of passing CO₂ rich solvent leavingthe Rotary Packed Bed (RPB) absorber to a Rotary Packed Bed (RPB) O₂eliminator; or, a static packed bed O₂ eliminator; and eliminating O₂from the solvent eliminates 90% or more of the O₂ present in the CO₂rich solvent.

Advantageously, each Rotary Packed Bed (RPB) has the followingdimensions: radius: from 0.2 m to 1.25 m, or from 0.2 m to 0.8 m; axiallength: from 0.02 m to 1.0 m, or from 0.2 m to 0.6 m; volume: from 0.04m³ to 4.9 m³, or from 0.04 m³ to 0.6 m³.

According to another aspect of the present invention, there is provideda system for capturing Carbon Dioxide (CO₂) from flue gases, the systemcomprising: at least one Rotary Packed Bed (RPB) absorber configured torotate circularly, wherein when the RPB rotates circularly a solventprovided through an inner radius of the at least one RPB absorber movestowards an outer radius of the at least one RPB absorber, and whereinthe solvent reacts with flue gas in a counter-current flow to captureCO₂.

Preferably, wherein the system further comprises: components forthermally regenerating the solvent reacted with the CO₂ for re-utilizingthe solvent in the process.

Further preferably, wherein the system further comprises: one or both ofa water wash and an acid wash, wherein passing the flue gas through oneor both of the water wash and the acid wash removes traces of thesolvent present in the flue gas.

Advantageously, wherein a housing of the RPB is mounted on a rotatabledisk.

Preferably, wherein the system comprises two, three, four, five or sixRotary Packed Bed (RPB) absorbers configured to rotate circularly.

Further preferably, wherein the two, three, four, five or six RotaryPacked Bed (RPB) absorbers configured to rotate circularly are arrangedin series on a common shaft.

Advantageously, wherein the solvent reacts with the flue gas in acounter-current flow to remove CO₂ from the flue gas and form CO₂ richsolvent.

Preferably, further comprising: a stripper, wherein the stripper isconfigured to strip CO₂ from the CO₂ rich solvent forming CO₂ leansolvent.

Further preferably, wherein the stripper is an RPB stripper.

Advantageously, wherein the system is configured to re-introduce the CO₂lean solvent into the at least one Rotary Packed Bed (RPB) absorberrotating circularly.

Preferably, further comprising: a Rotary Packed Bed (RPB) O₂ eliminator;or, a static packed bed O₂ eliminator; for eliminating O₂ from CO₂ richsolvent, the Rotary Packed Bed (RPB) O₂ eliminator; or, the staticpacked bed O₂ eliminator; positioned to eliminate O₂ from CO₂ richsolvent leaving the at least one Rotary Packed Bed (RPB) absorber.

Further preferably, wherein the Rotary Packed Bed (RPB) O₂ eliminator;or, a static packed bed O₂ eliminator; is configured to eliminate 90% ormore of the O₂ present in the CO₂ rich solvent.

Advantageously, wherein each Rotary Packed Bed (RPB) has the followingdimensions: radius: from 0.2 m to 1.25 m, or from 0.2 m to 0.8 m; axiallength: from 0.02 m to 1.0 m, or from 0.2 m to 0.6 m; volume: from 0.04m³ to 4.9 m³, or from 0.04 m³ to 0.6 m³.

The process as described in any one of paragraphs [0020] to [0032], orthe system as described in any one of paragraph [0033] to [0045],wherein the solvent comprises: a tertiary amine; and/or, a stericallyhindered amine; and/or, a polyamine; and/or, a carbonate buffer salt;and/or, water (optionally deionized water); optionally, water presentfrom 10 wt % to 70 wt %.

Preferably, wherein the solvent has a viscosity from 1 cp to 100 cp.

Further preferably, wherein the solvent: is any solvent disclosed in US2017/0274317 A1; and/or, the solvent comprises: a tertiary amine (forexample, N-methyl-diethanolamine and/or 2-(diethylamino)ethanol),and/or, a sterically hindered amine (for example,2-amino-2-ethyl-1,3-propanediol, 2-amino-2-hydroxymethyl-1,3-propanedioland/or 2-amino-2-methyl-1-propanol), and/or, a polyamine (for example,2-piperazine-1-ethylamine and/or 1-(2-hydroxyethyl)piperazine), and/or,a carbonate buffer (for example, potassium carbonate), and/or, water(for example, deionised water).

Advantageously, wherein the solvent comprises: an amino hindered alcohol(optionally, amino-2-methyl-1-propanol), a polyamine (optionally, aminoethyl piperazine) and water.

In another aspect of the present invention, there is provided anarrangement of Rotary Packed Bed (RPB) absorbers comprising two, three,four, five or six RPB absorbers configured to rotate circularly, whereinthe RPB absorbers are arranged in series on a common shaft.

In another aspect of the present invention, there is provided a vacuumsolvent reclamation system for removing Heat Stable Salts, degradationproducts and other contaminants from Carbon Dioxide (CO₂) capturesolvents, the vacuum solvent reclamation system comprising: a feedproduct exchanger configured to increase the temperature of CarbonDioxide (CO₂) capture solvents; a reboiler configured to furtherincrease the temperature of Carbon Dioxide (CO₂) capture solventsemitted from the feed product exchanger such that the Heat Stable Salts,degradation products and other contaminants accumulate in the reboiler;the feed product exchanger and the reboiler in fluid communication topermit batch or semi-batch removal of Heat Stable Salts, degradationproducts and other contaminants from the Carbon Dioxide (CO₂) capturesolvents; and, a condenser for decreasing the temperature of cleanedCarbon Dioxide (CO₂) capture solvents emitted from the feed productexchanger.

In another aspect of the present invention, there is provided a vacuumsolvent reclamation system for removing Heat Stable Salts, degradationproducts and other contaminants from Carbon Dioxide (CO₂) capturesolvents, the vacuum solvent reclamation system comprising a reboilerconfigured to increase the temperature of Carbon Dioxide (CO₂) capturesolvents drawn from the stripper reboiler, such that the Heat StableSalts, degradation products and other contaminants accumulate in thereboiler. The reboiler configured to permit batch or semi-batch removalof Heat Stable Salts, degradation products and other contaminants fromthe Carbon Dioxide (CO₂) capture solvents. The reboiler is incommunication with a condenser for decreasing the temperature of cleanedCarbon Dioxide (CO₂) capture solvents emitted from the reboiler.Advantageously, the reboiler and condenser may be in directcommunication.

Preferably, wherein the vacuum solvent reclamation system is in fluidcommunication with a system as described in any one of paragraphs [0033]to [0049].

In another aspect of the present invention, there is provided a processof capturing Carbon Dioxide (CO₂) from flue gases, the processcomprising the steps of:

-   -   providing a carbon capture solvent;    -   introducing the carbon capture solvent into a Rotary Packed Bed        (RPB) absorber and a Rotary Packed Bed (RPB) stripper; and,        optionally, an O₂ eliminator;    -   applying steam to a reboiler;    -   bringing the carbon capture solvent in the Rotary Packed Bed        (RPB) stripper to a desired pressure;    -   pumping the carbon capture solvent around the Rotary Packed Bed        (RPB) absorber and the Rotary Packed Bed (RPB) stripper;    -   introducing flue gas into the Rotary Packed Bed (RPB) absorber;    -   monitoring production of Carbon Dioxide (CO₂) from the Rotary        Packed Bed (RPB) stripper;    -   starting a Rotary Packed Bed (RPB) O₂ eliminator; or, a static        packed bed O₂ eliminator;    -   stopping the flow of flue gas to the Rotary Packed Bed (RPB)        absorber;    -   monitoring production of Carbon Dioxide (CO₂) from the Rotary        Packed Bed (RPB) stripper until Carbon Dioxide (CO₂) production        has stopped;    -   stopping supply of steam to the reboiler;    -   stopping circulation of the solvent;    -   stopping rotation of the Rotary Packed Bed (RPB) stripper,        absorber, water wash, acid wash and O₂ eliminator.

Embodiments of the present disclosure will be described more fullyhereinafter with reference to the accompanying drawings in which likenumerals represent like elements throughout the several figures, and inwhich example embodiments are shown. Embodiments of the claims may,however, be embodied in many different forms and should not be construedas limited to the embodiments set forth herein. The examples set forthherein are non-limiting examples and are merely examples among otherpossible examples.

FIG. 2 illustrates a block diagram 200 of a system for capturing CarbonDioxide (CO₂) from flue gases. At first, flue gas 202 may be fed into aRotary Packed Bed (RPB) absorber 204. A solvent may be fed through aninner radius of the RPB absorber 204. In the RPB absorber 204, packingmay be housed in a rotatable disk. The rotatable disk could be rotatedat high speed to generate centrifugal force. The centrifugal force maybe exerted upon the solvent when distributed onto the packing. Uponapplication of the centrifugal force, the solvent may move radially fromthe inner radius of the RPB absorber 204 towards an outer radius of theRPB absorber 204. The solvent may thus contact with the flue gas 202comprising CO₂, in a cross or counter-current configuration. Suchrotation of the RPB absorber 204 increases mixing between the flue gas202 and the solvent, leading to improved mass transfer of CO₂ present inthe flue gas 202 to the solvent present in the liquid phase.

Once the CO₂ is absorbed into the solvent, remaining flue gas may becleaned in one or more water wash units 206 and 208, and/or one or moreacid wash units 210. In one case, packed water wash sections can bereplaced with other RPB absorbers. Wash water may be fed from an innerradius of other RPB absorber and may flow radially across the packing toan outer radius of the other RPB absorber, under centrifugal forcegenerated by rotating motion. CO₂ depleted flue gas may be introducedfrom the outer radius of the other RPB absorber and may flow towards theinner radius of the other RPB absorber, thereby ensuring acounter-current contact between the wash water and the CO₂ depleted fluegas. A similar process could be applied to provide an acid wash bysubstituting water wash media for an appropriately concentrated solutionof acidic media. Cleaned flue gas 212 obtained upon washing may bevented to atmosphere.

In one embodiment, multiple RPB absorbers, i.e., a first RPB absorberand a second RPB absorber, may be used in place of the RPB absorber 204.The first RPB absorber and the second RPB absorber may have a smallerradius and may be arranged in series on a common shaft for removing theCO₂ present in the flue gas 202. The flue gas 202, a portion of whoseCO₂ has been removed in a first RPB absorber, is allowed to flow from anoutlet of the first RPB absorber to an inlet of a second RPB absorber.Inside the second RPB absorber, the flue gas 202 may be contacted crossor counter-currently with a lean solvent from the stripper. The flue gas202 obtained from the second RPB absorber may be depleted of CO₂ and maybe sent for a water wash before being emitted to the atmosphere. A richsolvent from the first RPB absorber may be sent to the stripper forregeneration.

In one embodiment, the solvent leaving the second RPB absorber andentering the first RPB absorber may be cooled in a heat exchanger 214 asthe solvent passes from the second RPB absorber to the first RPBabsorber. A solvent rich in CO₂ 216, exiting the RPB absorber 204, maybe sent to an RPB oxygen eliminator 218. The flue gas 202 present insidethe RPB absorber 204 may contain oxygen (O₂) which can react with thesolvent to form degradation products. This results in a requirement toremove and replace the degradation products formed from the solvent.Since the size of the RPB absorber 204 and RPB stripper 226 is muchsmaller than a static absorber and stripper, the residence time of thesolvent and gas are much shorter. Therefore, for each cycle of theprocess, degradation of the solvent occurs at a much lower rate.

In one embodiment, a portion of the oxygen (O₂) present in the flue gas202 may get absorbed into the solvent present inside the RPB absorber204. Such absorption of the O₂ is undesirable for many reasons includingoxidative degradation of the solvent and O₂ contamination of productCO₂. The dissolved O₂ may be removed from the rich solvent using the RPBO₂ eliminator; or, a static packed bed O₂ eliminator; 218. In this unitoperation, O₂ is stripped from the rich solvent by contacting a smallslipstream of product CO₂ gas from the rich solvent strippercounter-current to the solvent. Since the partial pressure of O₂ in theproduct CO₂ is low, dissolved liquid O₂ present in the solvent may gettransferred from the liquid solvent to the gaseous phase. A streamcontaining the dissolved O₂ in gaseous form 220 may be emitted from atop of the RPB O₂ eliminator 218; or, fed back to the RPB absorber 204.

The rich solvent, when it exits the RPB absorber 204, may have from 5 to10 mg/L of oxygen dissolved in it; or, from 10 to 15 mg/L of oxygendissolved in it. This oxygen causes degradation of the solvent in theheat exchanger 222 and RPB stripper 226. Thus, stripping O₂ from richsolvent as it exits the absorber is desired. The rich solvent flow is12,500 lb./h or 25 gpm. The Henry's constant of O₂ at 50° C. is ˜20,000atm/mole fraction. It is estimated that for 95% removal of O₂, a CO₂flow of 15 lb./hr is required. The oxygen removed would be ˜0.1 lb./hr.carried away by 15 lb./hr. of CO₂.

In one embodiment, the solvent may enter the RPB O₂ eliminator 218 froma center of a packed bed which is rotating. The solvent may be pushedfrom the center of the rotating packed bed to the outer radius due tocentrifugal forces, as described above. While the solvent leaves an edgeof the packing bed, the solvent strikes a wall of the casing of thepacking bed and then drains into a sump. A small portion of strippingCO₂ 240 may be fed through a penetration in the wall of the casing andpasses under pressure, counter currently, from the radius of the packedbed to the center of the packed bed. A penetration may be present at thecenter of the packed bed. The penetration may allow the gas to leave theRPB O₂ eliminator 218. Rotation of the packed bed may cause vigorousmixing of the solvent with the stripping gas. A CO₂ rich solvent 260 maythen exit the RPB O₂ eliminator 218 and may pass to a solvent heatexchanger 222.

In another embodiment, the CO₂ rich solvent may enter the conventional(static) packed bed O₂ eliminator 218 from the top of a packed bedcolumn. A small portion of stripping CO₂ 240 may be fed from the bottomof the packed bed column. The stripping CO₂ 240 may make counter-currentgas-liquid contact. A penetration may be present at the center of thepacked bed. The penetration may allow the gas to leave the conventionalpacked bed O₂ eliminator 218. A CO₂ rich solvent 260 may then exit theconventional (static) packed bed O₂ eliminator 218 and may pass to asolvent heat exchanger 222.

Once the CO₂ rich solvent 260 is heated in the solvent heat exchanger222 by the CO₂ lean solvent 242, a CO₂ rich solvent present at hightemperature 224 may be provided to an RPB stripper 226 and a reclaimedsolvent 228 may be fed back to the RPB absorber 204. The CO₂ richsolvent present at high temperature 224 may be fed into the RPB stripper226 through an inner radius of the RPB. The RPB stripper 226 may berotated to generate a centrifugal force exerted upon the CO₂ richsolvent present at high temperature 224 when distributed onto thepacking. Due to the centrifugal force, the CO₂ rich solvent present athigh temperature 224 may move radially from the inner radius of thepacking towards the outer radius of the RPB. While the CO₂ rich solventpresent at high temperature 224 moves from the inner radius to the outerradius, there may be a high degree of turbulent mixing and dropletformation which may increase the effective surface area for masstransfer. At the outer radius of the RPB, the CO₂ rich solvent presentat high temperature 224 may be ejected and accumulated in a solvent sumpvia the internal wall of RPB stripper casing.

In one embodiment, solvent 230 accumulated in the solvent sump may betransferred to a reboiler 232. The solvent 230 may be heated in thereboiler 232. A temperature inside the reboiler 232 may be set tovaporize water present in the solvent 230. The water may be vaporized atan operating pressure of the RPB stripper 226. Steam formed in thereboiler 232 may be introduced to the outer radius of the RPB stripper226.

In one embodiment, a take-off point may be present at the inner radiusof the RPB stripper 226 for receiving the steam and the CO₂ out of theRPB stripper 226. The steam and the CO₂ may be transferred to acondenser 234. Inside the condenser 234, the steam present with the CO₂may be condensed into a condensate 238, i.e., water. The water uponcondensation may be separated from the CO₂ in a reflux vessel 236.Condensation of the steam in the condenser 234 may cause a pressure dropto be induced across the stripper packing. Such pressure drop mayprovide a driving force for the water and the CO₂ to leave the RPBstripper 226. The CO₂ may be directed to a down-stream unit 240 fordown-stream processing.

In one embodiment, the condensate 238 may be mixed with the CO₂ richsolvent present at high temperature 224 before the condensate 238 entersthe RPB stripper 226 via the inner radius of the packed bed. A CO₂ leansolvent 242 produced in the reboiler 232 may be returned to the processthrough the solvent heat exchanger 222.

FIG. 3A illustrate a block diagram 300 showing functioning of a RotaryPacked Bed (RPB) absorber 302 in a system for capturing Carbon Dioxide(CO₂) from flue gases. At first, flue gas 304 may be fed to the RPBabsorber 302 and may be reacted with a solvent. The RPB absorber 302,placed on a rotatable disk, rotates and thus centrifugal force acts uponthe RPB absorber 302. The solvent may thus contact the flue gas 302comprising CO₂ in a cross or counter-current configuration. Once the CO₂is absorbed into the solvent, remaining flue gas may be cleaned usingwater wash and/or acid wash.

In one embodiment, wash water may be fed through an inner radius 306 ofthe RPB absorber 302. The wash water may thus flow radially, across apacking of the RPB absorber 302, to an outer radius of the RPB absorber302, under the action of the centrifugal force. During the water wash,CO₂ depleted flue gas to be processed may be introduced from the outerradius of the RPB absorber 302 and may flow towards the inner radius306, thereby ensuring a counter-current contact between the wash waterand the CO₂ depleted flue gas. Similarly, a concentrated solution ofacidic media may be used for providing the acid wash to the CO₂ depletedflue gas. Successive to the water wash and the acid wash, cleaned CO₂depleted flue gas 308 may be vented.

In one embodiment, multiple RPB absorbers, i.e., a first RPB absorberand a second RPB absorber, may be used in place of the RPB absorber 302.The first RPB absorber and the second RPB absorber may have a smallerradius and may be arranged in series on a common shaft for removing theCO₂ present in the flue gas 304 The flue gas 304 a portion of whose CO₂has been removed in a first RPB absorber, is allowed to flow from anoutlet of the first RPB absorber to an inlet of a second RPB absorber.Inside the second RPB absorber, the flue gas 304 may be contacted crossor counter-currently with a lean solvent from the stripper. The flue gas304 obtained from the second RPB absorber may be depleted of CO₂ and maybe sent for water wash before being emitted to the atmosphere. A richsolvent from the first RPB absorber may be sent to the stripper forregeneration.

In one embodiment, solvent rich in CO₂ 310, exiting the RPB absorber302, may be sent to an RPB O₂ eliminator 312. A portion of oxygen (O₂)present in the flue gas 304 may get absorbed into the solvent presentinside the RPB absorber 302 Such absorption of the oxygen (O₂) isundesirable for reasons stated above. The oxygen (O₂) may be removedfrom the rich solvent using the RPB O₂ eliminator 312. Since the partialpressure of O₂ in the product CO₂ is low, liquid dissolved O₂ present inthe solvent may get transferred to a gaseous phase. A stream 314 may beemitted from a top of the RPB O₂ eliminator 312. Successively, a CO₂rich solvent 316 may then exit the RPB deaerator 312 and may be providedto a solvent heat exchanger 318.

Once the CO₂ rich solvent 316 is heated in the solvent heat exchanger318 by the CO₂ lean solvent 350, a CO₂ rich solvent present at hightemperature 320 may be provided to an RPB stripper 322. A cooled CO₂lean solvent 324 to the RPB absorber 302 upon processing. The CO₂ richsolvent present at high temperature 320 may be fed into the RPB stripper322. The RPB stripper 322 may be rotated to generate a centrifugal forceexerted upon the CO₂ rich solvent present at high temperature 320 whendistributed onto the packing. Due to the centrifugal force acting uponthe RPB stripper 322, the CO₂ rich solvent present at high temperature320 may be ejected and accumulated in a solvent sump via the internalwall of RPB stripper casing.

In one embodiment, solvent 328 accumulated in the solvent sump may betransferred to a reboiler 330. The solvent 328 may be heated in thereboiler 330. Steam formed in the reboiler 330 may be introduced to anouter radius of the RPB stripper 322. A take-off point may be present atan inner radius of the RPB stripper 322 for receiving the steam and CO₂out of the RPB stripper 322. The steam and the CO₂ may be transferred toa condenser for condensing the steam present with the CO₂ into acondensate. The water upon condensation may be separated from the CO₂.Condensation of the steam in the condenser may cause a pressure drop tobe induced across the stripper packing. Such pressure drop may provide adriving force for the water and the CO₂ to leave the RPB stripper 322.The CO₂ 332 separated from the water may be directed for down-streamprocessing with a small portion of the CO₂ 332 may be fed into O₂eliminator 312.

In one embodiment, the cooled CO₂ lean solvent 324 may pass to the RPBabsorber 302 via a thermal reclaimer 326.

FIG. 3B illustrate a block diagram 3000 showing functioning of a RotaryPacked Bed (RPB) absorber 3020 in a system for capturing Carbon Dioxide(CO₂) from flue gases In one embodiment, as an alternative to theconfiguration of FIG. 3A, the thermal reclaimer 3260 may be positionedon a connecting point between the stripper reboiler 3300 and the solventheat exchanger 3180. In one embodiment, the solvent heat exchanger 3180and RPB absorber 3020 are in direct communication. The other componentsof the block diagram 3000 correspond to the components of the FIG. 3Awith a “0” added at the end of the respective reference number, e.g. 312in FIG. 3A is 3120 in FIG. 3B etc.

In one embodiment, Lean Solvent 402 from lean solvent cooler outlet maybe taken into a vacuum solvent reclamation system, as shown in blockdiagram 400 of FIG. 4A. The thermal vacuum solvent reclamation systemmay be operated to remove Heat Stable Salts (HSS), degradation products,and other contaminants from the solvent while the concentrations aremore than 2 wt. %. The vacuum solvent reclamation system may include aninput of the lean solvent 402 fed to a feed product exchanger 404. Thefeed product exchanger 404 increases temperature of the mixture from 40°C. to 165° C. by heating with vapors 412 from Reboiler 408.

The lean solvent 406 from the feed product exchanger 404 may then bepassed to a reboiler 408. The reboiler 408 may cycle thermic fluid inand out and may increase the temperature of the solvent from 165° C. to180° C. Sodium Hydroxide may be added in Reboiler 408 to liberate carboncapture solvent from heat stable salts and degradation products. In anembodiment, Residue 410 at the end of operation may be sent to anincinerator for disposal. Vapor components 412 of the mixture via thefeed product exchanger 404 may be provided to a condenser 416. The vaporcomponents 412 may be condensed into a liquid 418 before being sent toan absorber. The thermal reclaiming system may be operated in semi-batchmode allowing the HSS and impurities to accumulate in the reboiler 408.After the batch completion, water may be added in Reboiler 408 when theliquid level is low in order to facilitate the withdrawal of residue410.

In another embodiment, Lean Solvent 4020 from a lean solvent pumpdischarge may be taken into a vacuum solvent reclamation system, asshown in block diagram 4000 of FIG. 4B. The temperature of the LeanSolvent 4020 may be 120° C. The thermal vacuum solvent reclamationsystem may be operated to remove Heat Stable Salts (HSS), degradationproducts, and other contaminants from the solvent while theconcentrations are more than 2 wt. %. The vacuum solvent reclamationsystem may include an input of the lean solvent 4020 fed to a Reboiler4080.

The reboiler 4080 may circulate thermic fluid and may increase thetemperature of the solvent from 120° C. to 180° C. Sodium Hydroxide 4200may be added in Reboiler 4080 to liberate solvent from Heat Stable Saltsand degradation products. In an embodiment, demineralized water 4220 maybe added in Reboiler 4080. In an embodiment, medium pressure steam 4240may be added to Reboiler 4080 and medium pressure steam 4260 may beremoved from Reboiler 4080. Residue 4100 at the end of operation may besent to an incinerator for disposal. Vapor components 4120 of themixture may pass to a condenser 4160. In an embodiment, cooling water4300 may be added to condenser 4160 and cooling water 4320 may beremoved from condenser 4160. The vapor components 4120 may be condensedinto a liquid 4180 before being sent as treated solvent to an absorbervia a heat exchanger (not shown). The vapor components 4120 may be sentto an absorber via a vacuum pump 4280. The thermal reclaiming system maybe operated in semi-batch mode allowing the HSS and impurities toaccumulate in the reboiler 4080. After the batch completion, water maybe added in Reboiler 4080 when the liquid level is low in order tofacilitate the withdrawal of residue 4100.

An inherent advantage of using RPB strippers compared to the static bedstripper columns is increased mixing in the RPB strippers that resultsin better mass transfers of CO₂ from liquid to a gaseous phase. Thisenables utilization of an RPB stripper of much smaller size than aconventionally used stripper. Further advantages of utilizing the systemand the process for capturing Carbon Dioxide (CO₂) from flue gases mayinclude: lower energy requirement to capture unit mass of CO₂ due toless water in solvent, smaller and lower capital cost carbon captureplant due to higher rates of mass transfer, lower solvent degradationand make-up requirement due to shorter exposure to oxygen, lower energyrequirements to capture unit mass of CO₂ due to inter-stage coolingincreasing the CO₂ loading into the solvent, and lower solventdegradation and make-up requirements due to more uniform temperatureprofile in RPB absorber, shorter solvent residence time in the RPBabsorber and RPB stripper.

Further advantages of utilizing the system and the process for capturingCarbon Dioxide (CO₂) from flue gases may include: smaller size and hencelower capital cost for water wash and acid wash, reduced capital cost bymounting the RPB, absorber, water wash, acid wash, and stripper on asingle shaft, lower capital cost of oxygen eliminator, lower formationof aerosols due to removal of temperature bulge in RPB absorber, andutilization of vacuum thermal reclaimer and hence less degradation andhigh recovery of the solvent.

FIG. 5 illustrates a flowchart 500 of a process of capturing CarbonDioxide (CO₂) from flue gases, according to an embodiment. FIG. 5comprises a flowchart 500 that is explained in conjunction with theelements disclosed in FIGs. explained above.

The flowchart 500 of FIG. 5 shows the architecture, functionality, andoperation for capturing Carbon Dioxide (CO₂) from flue gases. It shouldalso be noted that in some alternative implementations, the functionsnoted in the blocks may occur out of the order noted in the drawings.For example, two blocks shown in succession in FIG. 5 may, in fact, beexecuted substantially concurrently or the blocks may sometimes beexecuted in the reverse order, depending upon the functionalityinvolved. In addition, the process descriptions or blocks in flow chartsshould be understood as representing decisions made by a hardwarestructure such as a state machine. The flowchart 500 starts at step 502and proceeds to step 526.

At step 502, recirculation of wash water and acid water may be startedin the process. At step 504, rotation of an RPB absorber and an RPBstripper may be started. Further, the presence of liquid solvent in areboiler and an absorber sump may be ensured at step 506. Steam may beapplied to the reboiler and stripper pressure may be allowed to reach aset point pressure at step 508. Recirculation of lean and rich solventrecirculation pumps may be started at step 510. The flow of flue gas maybe started into the process at step 512. Production of CO₂ from the RPBstripper may be monitored at step 514. Thereafter, RPB O₂ eliminator maybe started while product CO₂ is available from the RPB stripper at step516. The flow of the flue gas may be stopped at step 518. It may waituntil production of the product CO₂ stops at step 520. Supply of steamto the reboiler may be stopped at step 522, and recirculation of solventmay be stopped at step 524. Finally, rotation of the RPB stripper, RPBabsorber, water wash, acid wash, and O₂ eliminator may be stopped atstep 526.

FIG. 6 illustrates a block diagram 600 representation of a Rotary PackedBed Absorber test rig, according to an embodiment. The Rotary PackedAbsorber test rig allows for the testing of solvents under variousconditions, and allows temperature and flow to be measured at criticallocations. A simulated flue gas is created by mixing CO₂ 602 with air610 via mass flow controller 604 and mass flow controller 612,respectively. The simulated flue gas is fed into humidifier 606 whichhas a supply of hot water 614. The temperature of the simulated flue gaspost humidifier 606 is measured and controlled by temperaturemeasurement and controller 616. The simulated flue gas may then be fedinto Rotary Packed Bed Absorber 626. The Rotary Packed Bed Absorber hasan inner diameter of 0.08 meters and an outer diameter of 0.3 meters,providing a radial packed depth of 0.11 meters. The length of the packedbed along the axis of rotation is 0.02 meters. The Rotary Packed BedAbsorber 626 is housed in a poly propylene case with an internaldiameter of 0.36 meters. The Rotary Packed Bed Absorber 626 is driven bya synchronous electric motor with a maximum speed of 3000 rpm.

Rotary Packed Bed Absorber 626 is fed solvent from amine feed tank 608,where the solvent is heated by hot water system 622 at location 620 ofthe amine feed tank 608 using circulated hot water. The flow of thesolvent from amine feed tank 608 is measured at flow measurement 618 andthe temperature of the solvent from amine feed tank 608 is measured attemperature measurement 628. The temperature of the gas out 632 from theRotary Packed Bed absorber 626 is measured by temperature measurement630. The temperature of the amine out 636 is measured by the temperaturemeasurement 634.

EXAMPLES Example 1: Determining the Operating Conditions for a Range ofSolvents

In this example, the operating conditions for a range of solvents weredetermined. Table 1 shows the operating conditions for the solvents.

CO₂ absorption was measured for a range of solvent flow rates and speedsof rotation. The range of the parameter settings is shown in Table 1.

TABLE 1 The range of parameter settings for a range of solvents. Speedof rotation Liquid to gas ratio Solvent rpm kg/kg 30 wt. % Mono EthanolAmine 600-1450 2.8-3.7 90 wt. % Mono Ethanol Amine 600-1150 0.9-1.2 43wt. % CDRMax 600-1150 1.8-2.5 55 wt. % CDRMax 600-1450 1.5-2.4 43 wt. %CDRMax second pass 600-1150 1.8-2.5

For each test the inlet CO₂ 602 was constant at 12 mol. %, which is asimilar concentration to coal flue gas, and the temperature of theliquid solvent was 40° C. The liquid to gas ratio is a criticalparameter for a carbon capture process, as absorbers show higherperformance with an increased liquid flow rate until the absorberreaches its flooding point. An optimum flow rate may be found byconsidering the increased stripper duty required with increased amountsof solvent, which may be only lightly load with CO₂. The increasedstripper duty increases the necessary energy to perform the carboncapture process. The test results shown in Table 1 allow for thecalculation of the number of transfer units required (NTU_(OG)). Fromthe results on 30 wt. % MEA with a speed of rotation of 600 rpm and anL/G of 3.3, the inlet CO₂ was 12.1% and the outlet CO₂ was 9.1%.Therefore, the number of transfer units required is:

${NTU}_{OG} = {{\ln\frac{12.1}{9.1}} = 0.28}$

Further, the Packed Height is equal to the overall gas phase Height of aTransfer Unit (HTU_(OG)) multiplied by the Number of Overall Gas phasetransfer Units (NOG). Given that the radius of the test apparatus was0.11 m, the H=0.11 meters, and the NTU=0.28, the height of overall gasphase transfer unit is:

${HTU}_{OG} = {\frac{r_{o} - r_{i}}{{NTU}_{OG}} = {\frac{0.11}{0.28} = {0.39\mspace{14mu} m}}}$

The height of a gas transfer unit was found to be 0.39 meters. Thisshows a significant reduction in size of a gas phase transfer unit for aRotary Packed Bed absorber compared to a static bed absorber. Table 2shows the test results from five solvent trails, according to anembodiment.

TABLE 2 Test results from five solvent trials. 43 wt % 43 wt % 30 wt. %90 wt. % CDRMax CDRMax Solvent 55 wt % Solvent MEA MEA Solvent Secondpass CDRMax L/G (Liquid flow rate 3.30 1.10 2.20 2.20 1.90 to gas flowrate ratio) NTU 0.28 0.71 0.35 0.27 0.51 HTU 0.39 0.15 0.32 0.40 0.22Area of TU/m² 0.23 0.09 0.19 0.24 0.13 NTU required 2.30 2.30 2.30 0.232.30 Scale factor for 90% removal 8.22 3.24 6.58 8.53 4.51 Method 1 -Radius 0.90 0.36 0.72 0.94 0.50 radius basis Required/m Method 2 - Area1.93 0.30 1.23 2.07 0.58 area basis Required/m² Ro/m 0.82 0.35 0.67 0.850.47 Ri/m 0.04 0.04 0.04 0.04 0.04 Ro − Ri/m 0.78 0.31 0.63 0.81 0.43MEA = Mono Ethanol Amine, TU = transfer units, NTU = number of transferunits

For each solvent a range of liquid to gas ratio and speed of rotationwere tested. The testing provides a method for determining the size ofrotary packed bed absorber required for a 90% CO₂ capture at 600 rpm.

Example 2: Determining Operating Parameters Required to MaximizeRecovery of Solvents by Simulating the Vacuum Thermal Reclaimer

In this example, Table 3 illustrates the experimental results of avacuum thermal reclaimer system. A sample of solvent from an operatingCO₂ capture plant was reclaimed in an experimental setup. The recoveriesachieved are shown in Table 3. Furthermore, simulations were performedfor sensitivity analysis and optimize the operating parameters tomaximize the recovery and minimize the energy requirement.

TABLE 3 Experimental results of a vacuum thermal reclaimer system.Vacuum Thermal Reclaimer Experimental Results Inlet Recovered ParametersUOM Solvent Solvent Residue Recovery Total Sample wt % 100 98.1 1.998.1% CDRMax wt % 99.4 98.1 1.3 98.6% Heat Stable Salts wt % 0.6 0.0 0.60.0% UOM = unit of measurement

In this example, the operating parameters required to maximize therecovery of the solvent CDRMax was determined using a vacuum thermalreclaimer simulation. Table 4 illustrates a table showing the VacuumThermal Reclaimer Simulation Results, according to an embodiment. Theoptimum case results at a temperature of 165° C. and 0.75 bar(a) aretabulated in the table illustrated by Table 4.

TABLE 4 The vacuum thermal reclaimer simulation results. Inlet RecoveredParameters UOM Solvent Solvent Residue Recovery, % Total Flow kg/hr5235.9 4935.2 143.8 94.3% CO₂ kg/hr 157 157 0  100% CDRMax kg/hr 4999.74935.2 64.6 98.7% Heat Stable Salts kg/hr 79.2 0 79.2  0.0% UOM = Unitof measurement

Example 3: The Relationship of CO₂ in the Vapor Phase and the Loading(i.e. Concentration) of CO₂ in a Solvent at 40° C.

In this example, the relationship between CO₂ in the vapor phase and theloading (i.e. concentration) of CO₂ in a solvent at 40° C. wasdetermined. FIG. 7 illustrates a graph showing vapor liquid equilibrium(VLE) relationship between partial pressure of CO₂ in the vapor phaseand the loading (i.e. concentration) of CO₂ in a solvent at 40° C.

Example 4: Viscosity of Unloaded CO₂ Solvent and Loaded CO₂ Solvent

In this example, the viscosity of an unloaded CO₂ solvent and loaded CO₂solvent was determined. Table 5 shows unloaded (no CO₂) solventviscosity and CO₂ loaded solvent viscosity at 40° C.

TABLE 5 The viscosity of CO₂ loaded and unloaded (no CO₂) solvents. CO2loaded Viscositv, Unloaded cP @40 C. Viscosity, CO2 loading, Solvent cP@40 C. mol/L Viscosity, cP 40% DEEA + 10% AEP 4.472 2.000 12.59 10%AHPD + 10% AEP 1.370 0.597 1.78 10% AEPD + 10% AEP 1.470 0.658 1.86 30%AEPD + 15% AEP 3.759 2.020 8.77 30% AHPD + 15% AEP 4.004 2.050 10.62

In Table 5, the components are given in weight %. The balance in eachcase is demineralised water.

DEEA=2-(diethylamino)ethanol

AHPD=2-amino-2-hydroxymethyl-1,3-propanediol

AEPD=2-amino-2-ethyl-1,3-propanediol

AEP=2-piperazine-1-ethylamine

Example 5: Methodology of Sizing for RPB Scale Up

In this example, a design of a RPB that allows for a target of 10 tonsof CO₂ capture per day from a “coal style” flue gas that contains 10vol. % CO₂ at a capture rate of 90% was determined.

In this example, using empirical relationships, the inner diameter(d_(i)), outer radius (r_(o)), inner radius (r_(i)) and axial length (z)of an RPB are determined. The parameters are then used to determine thecross-sectional area and total volume of the RPB required.

In this example, the inner diameter (d_(i)) of the RPB was sized toinclude room for the liquid distribution mechanism, whilst avoidingliquid entrainment and excessive gas velocities during operation of theRPB.

In this example, the axial length (z) was determined to give the minimumpermissible sizing whilst allowing sufficient packing volume for therequired amount of mass transfer to take place without incurringflooding.

In conventional static systems the Height of the packing (H) requiredfor the specified degree of mass transfer is determined by the followingexpression. Where the Height of the packing (H) is the product of theoverall gas phase Height of a Transfer Unit (HTU_(OG)) and the Number ofTransfer Units for the gas phase (NTU_(OG)):H=NTU_(OG)HTU_(OG)

In RPB applications the packing requirements differ from conventionalstatic columns, as they are not linear with respect to height of thepacking. Instead, an analogy is used where the cross-sectional area ofthe packing (π(r_(o) ²−r_(i) ²)) is equivalent to Height of the packing(H) in a conventional system. This is expressed in relation to theoverall gas phase Area of a Transfer Unit (ATU_(OG)) and the overallNumber of Transfer Units for the gas phase (NTU_(OG)) in the followingequation:π(r _(o) ² −r _(i) ²)=NTU_(OG)ATU_(OG)

To determine the cross-sectional area of the packing ((π(r_(o) ²−r_(i)²)), both NTU_(OG) and ATU_(OG) must be known and can be derivedexperimentally using the following expressions, where y_(in) is theinlet mole fraction of the component to be absorbed; y_(out) is theoutlet mole fraction of the component to be absorbed; Q_(G) is thevolumetric gas flow; z is the axial length of the RPB and K_(G)a is thegas phase mass transfer coefficient:

${NTU}_{OG} = {\ln{\frac{y_{in}}{y_{out}}}}$${ATU}_{OG} = \frac{Q_{G}}{{zK}_{G}a}$

In this example, the solvent trials were carried out with a prototypeRPB absorber. A lean solvent with a CO₂ concentration of 0.1 mole of CO₂per mole of solvent alkalinity was used to simulate the expectedconditions in a real CO₂ capture plant. This resulted in gas phase masstransfer coefficients that were measured in conditions representative ofan operational CO₂ capture plant.

In the solvent trials for this example, the gas phase mass transfercoefficients had to be calculated. The cross-sectional area, axiallength, volumetric gas flow were already known, and the inlet molefraction of CO₂ in the gas (y_(in)) and outlet mole fraction of CO₂ inthe gas (y_(out)) were both measured.

In this example, by using the K_(G)a value for a solvent of interestallows the scaling of the radial depth to achieve 90% CO₂ capture from a10 vol. % CO₂ flue gas.

Example 6: Size of RPB to Capture 1 Ton Per Day CO₂

In this example, the size of a RPB that allows for a target of 1 ton ofCO₂ capture per day from a flue gas.

TABLE 6 Size parameters of a RPB that captures 1 ton of CO₂ per day froma flue gas that contains 10 vol. % CO₂ at a capture rate of 90%. RBPTechnology Radius Axial Length Volume Vessel m m m³ RPB Absorber 0.5740.064 0.033 RPB Stripper 0.144 0.024 0.002Table 6 shows that the dimensions of the RPB absorber and stripper areall less than one meter. The RPB absorber and stripper are relativelysmall and compact.

Example 7: Design of RPB to Capture 10 Tons of CO₂ Per Day

In this example, the design of a RPB that allows for a target of 10 tonsof CO₂ capture per day from a flue gas that contains 10 vol. % CO₂ at acapture rate of 90% was determined.

FIG. 8 illustrates a system for capturing CO₂ 1200. The system forcapturing CO₂ 1200 can be used to capture 10 tons of CO₂ per day. Thesolid lines in FIG. 8 depict the path of liquids, whilst the dashedlines depict the path of gases.

In this example, flue gas 1201 enters the system 1200 through inlet1201. In one example, the flue gas 1201 contains 10 vol. % CO₂ and is ata temperature of 140° C. The flue gas upon entering system 1200 may passthrough a fan 1202. The fan 1202 may be required to overcome thepressure drop in the ductwork as well as the downstream process.

In this example, two operations may be carried out in the system forcapturing CO₂ 1200.

In the first unit operation, the flue gas 1201 may be cooled in a DirectContact Cooler (DCC) 1203 by using a loop of water that passes throughDCC drum 1204, DCC recirculating pump 1205 and a heat exchanger/DCCcooler 1206. The DCC 1203 may be a RPB. The water may be cooled in aheat exchanger/DCC cooler 1206. Any excess condensate from the flue gas1201 may be purged via outlet 1207.

The second unit operation may be a SO_(x) column 1208, which may be usedto remove acid gas species such as SO_(x) and NO_(x) via an alkali wash.The SO_(x) column 1208 may be a RPB. A recirculating loop of waterpasses through SO_(x) drum 1209, SO_(x) recirculating pump 1210 andSO_(x) cooler 1211. The water may be dosed with an alkali 1212 by usinga dosing pump 1213. The water may contact the flue gas 1201 in theSO_(x) column 1208. Excess liquid may be purged from the loop via outlet1214.

In this example, the flue gas 1201 may then pass into a Carbon CaptureAbsorber vessel 1215. The Carbon Capture Absorber vessel 1215 may be aRPB. The flue gas 1201 may be contacted with a counter current carboncapture solvent. The Carbon Capture Absorber 1215 has two stages ofpacking in which the flue gas 1201 and carbon capture solvent arecontacted. Between the two stages of packing, the temperature of thecarbon capture solvent may be controlled by an intercooling heatexchanger composed of an intercooling exchanger 1218, intercooling pump1217 and intercooling drum 1216. The flue gas 1201, which may now bedepleted of CO₂, leaves the Carbon Capture Absorber and passes to aWater Wash vessel 1219. The Water Wash vessel 1219 may be a RPB. Thecarbon capture solvent, which may now be rich in CO₂, may leave theCarbon Capture Absorber via a Rich Solvent Drum 1220; from the RichSolvent Drum 1220 the carbon capture solvent enters an O₂ eliminator1222 via a Rich Booster Pump 1221.

In this example, the CO₂ depleted flue gas 1201 may enter the Water Washvessel 1219. In the Water Wash vessel 1219, the CO₂ depleted flue gas1201 may be contacted with two recirculating loops of water across twostages of Water Wash packing 1223 and 1226, which are configured inseries. Each loop of water 1223 and 1226 is circulated with a wash waterpump 1224 and 1227 and cooled in a heat exchanger 1225 and 1228 beforebeing returned to the Water Wash vessel 1219. The treated flue gas 1201may then pass out of outlet 1229.

In this example, the CO₂ rich carbon capture solvent enters the O₂eliminator 1222. The O₂ eliminator 1222 may be a RPB. In the O₂eliminator 1222, the CO₂ rich carbon capture solvent may be contactedwith a flow of carbon dioxide. The CO₂ and entrained oxygen may then bereturned to the Absorber 1215. The carbon capture solvent, which has hadoxygen removed, may be pump through a Surge Drum 1230, Rich Solvent Pump1231 and a Cross-over Heat Exchanger 1232 into the Stripper vessel 1233.A lean cooler 1242 may be positioned between the Cross-over HeatExchanger 1232 and the Absorber 1215.

In this example, vapor which is generated in a reboiler 1238 may be fedinto the Stripper vessel 1233 and used to heat and strip the CO₂ fromthe carbon capture solvent. The Stripper vessel 1233 may be a RPB. Avapor, comprised of steam, vaporized solvent components and CO₂ gas,from the Stripper vessel 1233 enters the Reflux Exchanger 1234 where itmay be reduced in temperature from 120° C. to 40° C. This causes steamand solvent components to condense into the liquid phase. The streamthen passes into the reflux tank 1235 where the gaseous CO₂ disengagesfrom the liquid components. The liquid components are then returned asreflux into the carbon capture solvent inventory. The liquid reflux maybe pumped by the Reflux Pump 1236 to the Stripper vessel 1233 while theCO₂ passes out of the Reflux Exchanger via outlet 1237 as a pure (>95%)stream of CO₂. A slipstream of the pure (>95%) stream of CO₂ is returnedto the O₂ eliminator 1222 where it acts as a purge gas in an O₂elimination process.

In this example, the operating pressure of the stripper vessel was 1bar(g) and the steam that entered the reboiler had an operating pressureof 3.5 bar(g) (saturated). The design pressure of the Stripper,Reboiler, Reflux Exchanger, Reflux Tank, Steam & Condensate system was10 bar(g).

In this example, the carbon capture solvent (that no longer containsCO₂) leaves the Stripper vessel 1233 via the reboiler 1238 where it maybe pumped using the Lean Solvent Pump 1239 through the Cross-over HeatExchanger 1232 and back into the Carbon Capture Absorber vessel 1215 viaa lean cooler 1242.

In this example, the DCC 1203, SO_(x) column 1208 and the Water Wash1219 may be situated on separate RPB shafts.

Example 8: Sizing RPB Process Equipment

In this example, process simulation software, such as ProTreat™ (asprovided by Optimized Gas Treating, Inc.), was used to size conventionalstatic technology and then the methodology of example 5 was used to sizethe RPB equipment.

Table 7 illustrates the comparative process equipment dimensions for aRPB and conventional static technologies that can capture 10 tons of CO₂per day from a 10 vol. % CO₂ flue gas source.

TABLE 7 comparative process equipment dimensions for a RPB andconventional static technologies that can capture 10 tons of CO₂ per dayfrom a 10 vol. % CO₂ flue gas source. Technology Type RPB AxialConventional (static) Radius Length Volume Diameter Height Volume Vesselm m m³ m m m³ DCC 0.52 0.34 0.28 0.72 5.00 2.04 SO₂ 0.32 0.29 0.10 0.725.00 2.04 Absorber CO₂ 0.72 0.23 0.38 0.67 12.00  4.23 Absorber O₂ 0.720.23 0.38 N/A N/A N/A Eliminator Stripper 0.25 0.23 0.05 0.43 8.00 1.16Water Wash 0.56 0.57 0.55 0.63 6.00 1.87

Table 7 shows comparative data for the equipment dimensions of a RPB anda conventional static equivalent technology. Table 7 shows that thevolume of the packing required to achieve 90% CO₂ capture for the RPBprocess equipment is reduced by, or close to, an order of magnitude.

Example 9: Sizing Auxiliary Process Equipment Used in RPB ContainingSystem

In this example, process simulation software, such as ProTreat™ (asprovided by Optimized Gas Treating, Inc.), was used to size auxiliaryprocess equipment used in an RPB containing system according to example8.

Tables 8, 9 and 10 illustrate the equipment dimensions for a RPBtechnology that can capture 10 tons of CO₂ per day from a 10 vol. % CO₂flue gas source. In the tables, the specification of the pumps, fans,heat exchangers and tanks required for such a plant is shown.

TABLE 8 Specification parameters of pumps and fans for RPB technology.Operating Discharge Material Capacity Temperature Pressure Power of NameType m³ hr⁻¹ ° C. bar(a) kW construction DCC Recirc. Centrifugal 14.8N/A 4.3 2.35 304 SS Pump SOx Recirc. Centrifugal 14.8 43 4.3 2.35 304 SSPump Rich Solvent Centrifugal 5.6 46 5.8 1.2 304 SS Pump Lean SolventCentrifugal 6 120 4.4 0.95 304 SS Pump Gas Booster Centrifugal 3,700 1500.13 (dP) 17 304 SS Fan Water Wash Centrifugal 5.1 60 2.7 0.51 304 SSRecirc. Pump 1 Water wash Centrifugal 6.1 40 3.2 0.74 304 SS Recirc.Pump 2 Water wash Centrifugal 0.23 40 2.0 0.02 304 SS condensate PumpSteam Centrifugal 0.7 140 3.3 0.1 304 SS Condensate Pump Reflux PumpCentrifugal 0.28 120 3.4 0.04 304 SS Solvent Makeup Centrifugal/ 0.2Ambient 1.8 0.01 304 SS PD pump Alkali Dosing Centrifugal 0.2 Ambient1.8 0.01 304 SS Pump Rich Booster Centrifugal 5.6 46 2 0.5 304 SS PumpIntercooling Centrifugal 4.6 55 2.7 0.46 304 SS Pump

TABLE 9 Specification parameters of heat exchangers for RPB technology.Heat Design Duty Pressure Name Type MJ hr⁻¹ bar(g) MoC DCC Cooler Plateand Frame 950 3.0 SS304L SO_(x) Cooler Plate and Frame 172 3.0 SS304LIntercooling Exchanger Plate and Frame 239 4.5 SS304L Cross-over HXPlate and Frame 1372 5.0 SS316L Reflux Exchanger Shell and Tube 580 2.0SS304L Lean Cooler Plate and Frame 183 4.5 SS304L Water Wash Cooler 1Plate and Frame 252 3.5 SS304L Water Wash Cooler 2 Plate and Frame 3083.5 SS304L Stripper Reboiler Kettle Type 1560 1.0 SS316L

TABLE 10 Specification parameters of tanks for RPB technology. OperatingOperating Volume Temperature Pressure Name m³ ° C. bar(g) MoC DCC Drum0.3 56 0 304 SS SOx Drum 0.3 44 0 304 SS Intercooling Drum 0.09 61 0 304SS Rich Solvent Drum 0.12 46 0 304 SS WW Drum 1 0.1 58 0 304 SS WW Drum2 0.12 50 0 304 SS Surge Drum 0.12 46 0 304 SS Reflux Tank 0.12 120 1304 SS Solvent Storage Tank 2.60 40 0 304 SS Steam Condensate N/A N/AN/A CS + 1.5 Drum mm CA

The present application shows that the volume of the packing required toachieve 90% CO₂ capture for the RPB process equipment is reduced by, orclose to, an order of magnitude. This is beneficial at least because ofthe reduction in capital expenditure and reduction in size in providingthe same or a greater CO₂ capture capability. Utilising RPBs asdescribed in the present application provides benefits over knownsystems.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutions,and alterations can be made herein without departing from the disclosureas defined by the appended claims. Moreover, the scope of the presentapplication is not intended to be limited to the particular embodimentsof the process, machine, manufacture, composition of matter, means,methods and steps described in the specification. As one will readilyappreciate from the disclosure, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized. Accordingly, the appended claims areintended to include within their scope such processes, machines,manufacture, compositions of matter, means, methods, or steps.

When used in this specification and claims, the terms “comprises” and“comprising” and variations thereof mean that the specified features,steps or integers are included. The terms are not to be interpreted toexclude the presence of other features, steps or components.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

The invention claimed is:
 1. A process of capturing Carbon Dioxide (CO₂)from flue gases, the process comprising the steps of: (a) providing acarbon capture solvent; (b) introducing the carbon capture solvent intoa Rotary Packed Bed (RPB) absorber and a Rotary Packed Bed (RPB)stripper; (c) applying steam to a reboiler; (d) bringing the carboncapture solvent in the Rotary Packed Bed (RPB) stripper to a desiredpressure; (e) pumping the carbon capture solvent around the RotaryPacked Bed (RPB) absorber and the Rotary Packed Bed (RPB) stripper; (f)introducing flue gas into the Rotary Packed Bed (RPB) absorber; (g)monitoring production of Carbon Dioxide (CO₂) from the Rotary Packed Bed(RPB) stripper; (h) starting a Rotary Packed Bed (RPB) O₂ eliminator;or, starting a conventional packed bed O₂ eliminator; (i) stopping theflow of flue gas to the Rotary Packed Bed (RPB) absorber; (j) monitoringproduction of Carbon Dioxide (CO₂) from the Rotary Packed Bed (RPB)stripper until Carbon Dioxide (CO₂) production has stopped; (k) stoppingsupply of steam to the reboiler; (l) stopping circulation of the carboncapture solvent; (m) stopping rotation of the Rotary Packed Bed (RPB)stripper, absorber, and O₂ eliminator.
 2. The process of claim 1,wherein the process further comprises the step of: thermallyregenerating the carbon capture solvent reacted with the CO₂ forre-utilizing the carbon capture solvent in the process.
 3. The processof claim 1, wherein the process further comprises the step of: passingthe flue gas through one or both of a water wash and an acid wash toremove traces of the carbon capture solvent present in the flue gas; andstep (m) further comprising stopping rotation of the water wash, theacid wash, or, when both are present, both.
 4. The process of claim 3,wherein one or both of the water wash and the acid wash are conducted onseparate Rotary Packed Beds (RPBs).
 5. The process of claim 1, wherein ahousing of at least one of the RPBs is mounted on a rotatable disk. 6.The process of claim 1, wherein the step of introducing the flue gascomprising CO₂ to the Rotary Packed Bed (RPB) absorber comprises feedingthe flue gas to two, three, four, five or six Rotary Packed Bed (RPB)absorbers.
 7. The process of claim 6, wherein the two, three, four, fiveor six Rotary Packed Bed (RPB) absorbers are arranged in series on acommon shaft.
 8. The process of claim 1, wherein the carbon capturesolvent reacts with the flue gas in a counter-current flow to remove CO₂from the flue gas and form CO₂ rich solvent.
 9. The process of claim 8,wherein the Rotary Packed Bed (RPB) stripper produces a CO₂ lean solventfrom the CO₂ from the CO₂ rich solvent.
 10. The process of claim 9,wherein the RPB stripper is a stripper column, a stripper static column,or a RPB stripper.
 11. The process of claim 9, wherein the CO₂ leansolvent is re-introduced into the Rotary Packed Bed (RPB) absorber. 12.The process of claim 1, wherein the Rotary Packed Bed (RPB) O₂eliminator or conventional packed bed O₂ eliminator eliminates 90% ormore of the O₂ present in the CO₂ rich solvent formed from the RotaryPacked Bed (RPB) absorber.
 13. The process of claim 1, wherein eachRotary Packed Bed (RPB) has the following dimensions: radius: from 0.2 mto 1.25 m, or from 0.2 m to 0.8 m, axial length: from 0.02 m to 1.0 m,or from 0.2 m to 0.6 m, volume: from 0.04 m³ to 4.9 m³, or from 0.04 m³to 0.6 m³.
 14. The process of claim 1, wherein the carbon capturesolvent comprises at least one of a tertiary amine a sterically hinderedamine a polyamine, a carbonate buffer salt, water, or a combinationthereof.
 15. The process of claim 14, wherein the carbon capture solventhas a viscosity from 1 cp to 100 cp.
 16. The process of claim 14,wherein the carbon capture solvent comprises at least one of: a tertiaryamine, a sterically hindered amine, a polyamine, a carbonate bufferwater, or a combination thereof.
 17. The process of claim 16, wherein atleast one of: (a) the tertiary amine is N-methyl-diethanolamine,2-(diethylamino)ethanol, or a combination thereof; (b) the stericallyhindered amine is 2-amino-2-ethyl-1,3-propanediol;2-amino-2-hydroxymethyl-1,3-propanediol; 2-amino-2-methyl-1-propanol, ora combination thereof; (c) the polyamine is 2-piperazine-1-ethylamine,1-(2-hydroxyethyl)piperazine, or a combination thereof; (d) thecarbonate buffer is potassium carbonate; (e) the water is deionisedwater; or (f) a combination thereof.
 18. The process of claim 14,wherein the carbon capture solvent includes water, an amino hinderedalcohol and a polyamine.
 19. The process of claim 18, wherein the aminohindered alcohol is amino-2-methyl-1-propanol, the polyamine is aminoethyl piperazine, or a combination thereof.
 20. The process of claim 14,wherein the water is present in the carbon capture solvent in an amountfrom 10 wt % to 70 wt. % of the carbon capture solvent.
 21. The processof claim 1, wherein step (b) or step (h) further includes introducingthe carbon capture solvent into an O₂ eliminator.